Had fruit on it. Dark purple skin, size of a golfball, with orange flesh. Definitely related to peach/nectarine etc but not sure what it is exactly.

...and the tree is located in which city/state/country?

It is in Merano in Northern Italy. It is a cultivated tree though, not a wild one

Can you post a photo of the leaves? It reminds me of Plum, maybe a variety of Prunus domestica: http://garden.org/plants/searc...

Fruit images for comparison: Prunus domestica fruit images

Could be Empress prune plum which is popular in Italian home gardens. Prunica domestica "Empress".

http://www.specialtyproduce.co...

I submitted a proposal to add 'Empress' to our database since I couldn't find it listed there.

Damsons maybe? (No such plant as Prunica, Greene, I too saw that in Google results when I searched for "Empress" but I think someone mis-spelled Prunus and it was perpetuated from there).

Damsons:
https://www.google.ca/search?q...

I'm not sure that 'Empress' is an actual cultivar of plum rather than a type?

Maybe I jumped the gun then, proposing to add it to the database. @zuzu, can you decline my proposal, please?

Lin, it may be sold as a cultivar but when I did some Googling for that this morning I didn't find anything to support that, I saw mostly "also sold as". So don't write it off just yet - we could do some more checking, I didn't have time to pursue it after a quick looking this morning.

sooby said: No such plant as Prunica, Greene...

Thank you for the correction. I know it's supposed to be prunus but offered the spelling as prunica even though it is incorrect because there are several search results with good information about this tree using the "wrong" spelling.

Here is a site that offers several of the European type plum trees. Maybe this will help to identify the mystery tree in Italy.
https://www.grandpasorchard.co...